This invention relates generally to mass spectrometers, and more particularly to a mass spectrometer having a plurality of ionization probes.
Atmospheric pressure ionization (API) sources including electrospray (ES) and atmospheric pressure chemical ionization (APCI) sources which are interfaced with a mass spectrometer have typically operated with a single sample probe. U.S. Pat. No. 5,668,370 describes a mass spectrometer with a plurality of API sources. There is described an API source which includes an ES and an APCI probe which can be selectively brought opposite the input aperture of a mass spectrometer. A relatively complex mechanical arrangement is required to bring the probes opposite the input aperture.
International Publication No. WO 99/13492 describes an API source which includes a plurality of probes directed at a capillary tube which conveys samples into a mass spectrometer. The individual probes are selectively operated to sequentially introduce sample ions into the capillary or they can be simultaneously operated to provide sample ion mixtures to the capillary tube. The fact that the sample applied to the probes is selectively turned on and off may result in clogging of the sample probe.
There is a need for a sample multiprobe API source in which the sources are continuously operated and the ionized sample reaching the coupling orifice is controlled or switched to arrive from selected sources.
It is a general object of the present invention to provide a multiprobe API source in which the sources are selectively coupled to the mass spectrometer inlet aperture or capillary.
It is another object of the present invention to provide a multiprobe API source in which the individual probes are coupled to the inlet aperture or capillary via gas passages in which the passage of ions can be selectively blocked to thereby selectively connect the probes to the inlet aperture or capillary.
The foregoing and other objects of the invention are achieved by a mass spectrometer in which a plurality of API source probes are coupled through an inlet aperture or capillary to the low pressure region of the mass spectrometer by individual conduits which include means for selectively blocking the flow of ions from the associated probe whereby ions from selected probes enter the aperture or capillary.